ex B being non empty strict subcategory of W -INF_category st
( ( for a being object of (W -INF_category ) holds
( a is object of B iff S₁[a] ) ) & ( for a, b being object of (W -INF_category )
for a', b' being object of B st a' = a & b' = b & <^a,b^> <> {} holds
for f being Morphism of a,b holds
( f in <^a',b'^> iff S₂[a,b,f] ) ) ) from YELLOW18:sch 7(A1, A2, A5);
hence ex b₁ being non empty strict subcategory of W -INF_category st
( ( for a being object of (W -INF_category ) holds a is object of b₁ ) & ( for a, b being object of (W -INF_category )
for a', b' being object of b₁ st a' = a & b' = b & <^a,b^> <> {} holds
for f being Morphism of a,b holds
( f in <^a',b'^> iff @ f is directed-sups-preserving ) ) ) ; :: thesis: verum